Manufacture of artificial silk and other artificial products



. b i of t present invention, t a a pinning therewith, we find that the draw-down .of the 20 40 practically solvents, as for example methylen cussed above. Other cellulose esters, as .for ex- 40 -55 tions thereof, and also the lower fractionskof tion of the filaments no matter what concentra- Patented June 23, 1936 v a a .i a 3 MANUFACTURE OF ARTIFICIAL SILK AND 'OTHER ARTIFICIAL PRODUCTS Henry Dreyfus, London, and William Ivan Taylor, Spondon, near Derby, England, assignors to Celanese Corporation of America, a corporation of Delaware I No Drawing. .Application July 1, 1932, Serial No. 620,548. In Great Britain August 19, 1931 13 Claims. (Cl. 1854) This invention relates to the'manufacture. of gasoline and other low boiling hydrocarbons, may filaments, threads, yarns and the like'from solube employed.

tions of cellulose acetate or other cellulose esters The volatile liquid may be added in any Suitable or others by the dry spinning or evaporative proportion in relation to the cellulose derivative method. or to the main bulk of solvent or solvent mixture 5 It is well known that in the early days of the used. In employing non-solvents it will be apcellulose acetate artificial silk industry considerpreciated that the proportion of volatile liquid able dimculties arose from the fact that fabrics to be added is limited by considerations of the made from such filaments exhibited the disadsolubility of the cellulose derivative in the mixvantage of scintillation, and it was found that ture of solvent and volatile liq d- We aVe b- 10 this was due at least in part to the relatively tained very good results by dissolving anacetonefiat cross-section which the filaments exhibited; s u cellulose a at n a mixture s st These difilculties were overcome to a large extent of 6 to 1 o diet yl et er d 94 t0 o by the use of spinning solutions containing upacetone. Similarproportions may be used in the wards of and particularly or more, of case of petrol ether, though it has been found 15 cellulose acetate, (see U. S; Patent No. 1,688,531). that DIOIJOItiOIIS f a d unde w 130 The present invention is likewise concerned with even 1655, are preferablemethods for improving the cross-section of the If Water be included in a p nn n solution onfilaments. We'ha f nd, a d thi form t taining a solvent or solvent mixture miscible solution containing a volatile constituent in addifilaments is thereby improved- Similarly methyl tion to the liquid f r ihg'th main bulk of t or .ethyl alcohol and like liquids will improve the solvent or solvent mixture is capable of yielding dIaWPdOWH, though to a SS e tent than water. filaments which are very much rounder than the The P e invention therefore e a es the 25 filaments obtained from such a solution in the spinning f a s lution c t n n addition to 25 ab n of th 1 t11 t tu t the main bulk of solvent or solvent mixture and According t t r t invention, therefore the volatile liquid characteristic of the invention, artificial filaments, threads, -yarns-and=the like a ploportieni for p e 3 t0 even p to of improved cross-section are obtained by dry 10%, of Water other liquid adapted to p ve spinning processes from solutions containing a the aw'down 0f h filaments- For a e, 30 volatile constituent in addition to the solvent or We have Obtained highly Satisfactory su ts by l t mixture fonning t main bulk of the dissolving an acetone-soluble cellulose acetate in spinning solution. a mixture containing 86% of acetone,- 6% of The volatile agents employed'fo'r. the purpose of Water and 8% of diethyl ether the present invention may be solvents for the The process 0 e present invention isflapable 35 cellulose derivative, as for example methyl or of being pp to Spinning Solutions of all ethyl formate in the case of acetone-solublecellukinds, and the invention is not limited to 1 t t spun from t n Sohltiohs, 1 tone solutions of acetone-soluble cellulose acesolvents, that is to say substances whichare ietee Which have been more cula y schloride in the case of acetone-soluble cellulose ucellulose fermeie, cellulose p p t acetate, weakly acting precipitants or substances Cellulose butyrate and the like a mixed est which are swelling or gelling agents for'the cellueXample Cellulose acetate-bullyrate a d 81- lose derivatives, or strongly acting p-reoi giitant lulose nitro-acetate, and also cellulose ethers, as

for the cellulose derivative. Precipitants, and forexemnle ethyl or benzyl ce lu ose, ethyl-ben- 45 especially t 1 acting precipitantsfare t -zyl cellulose or other mixed ethers and mixed most useful liquids for the purposes of the present ether-esters of cellulose, y mployed. Euroi tie I thi la t categbry'we "ha found ther, instead of using acetone as the solvent that the ethers, and particularly .dieth l eth 'or the main bulk of the solvent, mixtures of aceareiespecially valuable; Otherethe-rs which may e and 31001101, acetone and methyl alcohol} '50 be employed are methyl or ethyl propyl ether, ethyl or methyl acetate and ethyl or methyl al- .ethyl isopropyl 'ether and 'dieisopropyl ether. cohol, or mixtures of anyof these solvents may Furthermore the low boiling fractions .of be employed, or indeed any other suitable solpetroleum, and particularly petrol ether or fracvents. The invention improves the cross-section of spinning solution may be employed, that is to say that even when employing concentrations of 25% or higher in the spinning solution, improved cross-sections are obtainable. However, the maximum advantage of the present invention is attained in the case of spinning filaments from solutions of lower concentration, as for example 25 to 20 or 15% or less by weight of the cellulose derivative. The ability to improve the cross-sections of filaments obtainable from these lower concentrations is of especial advantage in the case of spinning at the modern high speeds, such as 200 to 300 or 400 or more metres per minute, though advantages still accrue from the employment of the older lower spinning speeds, such as 150 or metres per minute. With the higher spinning speeds it is found that the draw-down of the filaments is not as good as in the case of spinning the same spinning solutions through the same jet orifices gat. lower spinning speeds, which is a disadvantage in view of the commercial demand for low .filament deniers. By enabling filaments of round cross-section to be obtained from solutions of relatively low concentration, the present invention makes it possible to obtain low filament deniers of good cross-section at the modern high spinning speeds, and the process of the invention is therefore extremely valuable in this connection.

In order to improve still further the cross-sec- .tion and other valuable characteristics of the filaments cellulose derivatives, and particularly cellulose acetates, of high viscosity character- ;-istics, .for example those obtained by the process described in U. S. Patent No. 1,829,822, may be used. The present invention includes therefore the use of these cellulose derivatives in the special spinning solutions described above.

' Furthermore, we have found that for the purpose of obtaining good cross-sections it is of .great importance to promote a rapid evaporation inthe very early stages of spinning by the dry spinning method. For example, we have found that if a rapid evaporation of the solvent 1 or solvent mixture be brought about within the first two inches of the travel of the filaments athrough the usual dry spinning cell, better crosssections are obtain-able than if evaporation is allowed to proceed normally. The figure of two inches is given in relation to the usual type of :dry spinning cell in which the travel of the filaments is about six or seven feet within the spinning cell. The figure appears to be critical, since a rapid evaporation at a distance of three inches from the nozzle does not produce thesame 'ef- It is probably for this reason that the ethers and other highly volatile liquids have a beneficial effect upon the cross-section of the filaments. In order to improve this effect still further other means may be adopted to induce a rapid evaporation in the very early stages of the spinning. .For example, it is of great advantage to cause a current of evaporative medium'to cross the face of the nozzle or, otherwise introduce fresh evaporative medium in the'immediate vicinity of the nozzle, (compare U. S. application S. No. 382,907 filed 2nd August, 1929),. The evaporative medium so introduced .may be heated or not and may be directed to- Wards'the filaments from one side only or from two or more points of the spinning cell or from .the centre of the nozzle so as to blow across the filaments in a radial direction when employing jet. orifices arranged in a ring, as in the ring type or disc type nozzle. Furthermore, greater evaporation may be induced by employing the collector devices of U. S. applications S. Nos. 236,448 filed 29th November, 1927, 311,213 filed 8th October, 1928, 311,214 filed 8th October, 1928, 5 405,784 filed 8th November, 1929, and 495,140 filed 12th November, 1930. Again a very rapid evaporation in the early stages of spinning may be achieved by employing a vacuum or sub-atmospheric pressure in the spinning cell or chain- 10 her as described and claimed in U. S. application S. No. 375,150 filed 1st July, 1929. A combination of two or more of the above devices may be effected in order to improve still further the evaporation. l 3

All the above advantages of the present invention may be obtained by means of jet orifices of the-normal size, for example .05 to .08 or .10 millimetre diameter. Jet orifices of larger crosssection or of smaller cross-section down to the minimum'obtainable may, however, be used.

The following examples are given to illustrate the invention, but it is to be clearly'un-derstood that they do not limit it in any way.

Example 1 A solution of cellulose acetate, of about 20-21% concentration, in an acetone-diethyl ether mixture containing about 88% of acetone and 12% of diethyl ether is spun through jets of .055 millimetrediameter at a spinning speed of from 200-250 metres per minute. Filaments of low denier, for example, from 2-3 deniers having a good cross-section are obtained; Example 2 A cellulose acetate solution of from 22-23% concentration in a mixture consisting of about 8% diethyl ether, 86% acetone and 6% water is spun under similar conditions to those obtaining in 0 Example 1, and filaments of 10W denier and good "cross-section are obtained.

Example 3 A 23-26% solution of cellulose acetate in a solvent mixture consisting of from 6-10% iso-,....

p'ropyl ether and 94-90% acetone is spun through jets of .07 millimetre diameter at a speed of -200 metres per minute, yielding filaments of improved cross-section.

The'invention has been described above more CO particularly in relation to the manufacture of filaments, in which it is of the greatest value.

Nevertheless advantages accrue by employing the process of the invention for the manufacture of other types ofproducts, for example ribbons. What We claim and desire to secure by Letters Patent is 1. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a 70 solution of an organic derivative of cellulose in a solvent mixture comprising a liquid medium 'which is a solvent for the organic derivative of cellulose and a. smaller proportion of a more vola- .tilenon-solvent for the organic derivative of cel- 7 5 lulose, and extruding said solution through suitable orifices into an evaporative atmosphere.

2. Process for the production of solid artificial filaments, threads and the like of irnjproved bulbous cross-section, which comprises forming a solution of cellulose acetate in a solvent mixture comprising a solvent for the cellulose acetate and not more than 12%, based on the solvent mixture, of a more volatile non-solvent for the cellulose acetate and extruding said solution through suitable orifices into an evaporative atmosphere.

3. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of an organic derivative of cellulose in a solvent mixture comprising a solvent for the organic derivative of cellulose and not more than 12 based on the solvent mixture, of an aliphatic ether which is more volatile than the said solvent, and extruding the said solution through suitable orifices into an evaporative atmosphere.

4. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of cellulose acetate in a solvent mixture comprising a solvent for the cellulose acetate and a smaller proportion of diethyl ether, the said solvent being less volatile than diethyl ether, and extruding said solution through suitable orifices into an evaporative atmosphere.

5. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of cellulose acetate in a solvent mixture containing acetone and diethyl ether, the proportion of diethyl ether being between 6 and 12% of the solvent mixture, and extruding said solution through suitable orifices into an evaporative atmosphere.

6. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of an organic derivative of cellulose in an aqueous solvent mixture comprising a solvent for the organic derivative of cellulose and a smaller proportion of an aliphatic ether which is more volatile than the said solvent, and extruding said solution through suitable orifices into an evaporative atmosphere.

'7. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming an 18 to 25% solution of cellulose acetate in a solvent mixture comprising acetone and a smaller proportion of diethyl ether, extruding said solution through suitable orifices, and drawing off the products at a speed greater than metres per minute.

8. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of cellulose acetate of relatively high viscosity characteristics in a solvent mixture comprising acetone and a smaller proportion of diethyl ether, extruding said solution through suitable orifices and drawing off the products at a speed greater than 150 metres per minute.

9. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of an organic derivative of cellulose in a solvent mixture comprising a solvent for the organic derivative of cellulose and a smaller proportion of an aliphatic ether which is more volatile than said solvent, extruding the said solution through suitable orifices into an evaporative atmosphere, and inducing rapid evaporation of the solvent mixture near the extrusion orifices.

10. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of cellulose acetate in a solvent mixture comprising acetone and a smaller proportion of' diethyl ether, extruding said solution through suitable orifices into an evaporative atmosphere, and inducing rapid evaporation of the solvent mixture near the extrusion orifices.

11. Process for the production of solid artificial filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of cellulose acetate in a solvent mixture comprising a solvent for the cellulose acetate and a smaller proportion of a more volatile non-solvent for thecellulose acetate selected from the group consisting of methyl propyl ether, ethyl propyl ether, ethyl isopropyl ether, di-isopropyl ether and petroleum ether fractions boiling above 40 (3., and extruding the said solution through suitable orifices into an evaporative atmosphere.

filaments, threads and the like of improved bulbous cross-section, which comprises forming a solution of cellulose acetate in a solvent mixture comprising acetone and a smaller proportion of a petroleum ether fraction boiling above 40 C.

but being more volatile than acetone, and extruding the said solution through suitable orifices into an evaporative atmosphere.

HENRY DREYFUS. WILLIAM IVAN TAYLOR. 

